I'm relatively new to the ZJ world. Owned a Cherokee, but replaced it with my 96 Grand. Within a week of owning the ZJ, I took it offroad. I doubt seriously if it has ever been offroad. Shortly after, the "Part Time" light shows up (I have the Select Track) while the lever is still in the 2WD position. Even if I pull the lever back into the PT position, then push it forward again, it usually stays lit. The front wheels on the center console display will often turn blue. If I pull it back to FT 4WD, drive it like that for a bit, then shift it back to 2WD when I'm going in a straight line down the road at speed, it will usually go back to 2WD. It's annoying, but I'm learning to live with it.
So you guys are thinking this is a linkage problem?